What is the key to design the stiffener of automobile sheet metal parts?

2019-12-31 10:28:49

Stiffeners are widely used in the manufacturing industry, as well as in the automotive industry. Many car body sheet metal are equipped with stiffeners, except for the appearance surface with special requirements. The role of stiffeners is to enhance the strength and stiffness of some areas, improve the characteristics of noise, vibration and acoustic vibration roughness (NVH). In addition to the important parts, the daily installed stiffeners have little impact on the use of vehicles, so the design and application of stiffeners in the automotive industry are not as good as the collision ability, lightweight and other similar functions, which have received too much attention. In addition, the stiffeners on automobile sheet metal include automobile and mechanical properties, which are rarely involved in all kinds of automobile and mechanical data. Therefore, although there are many applications of stiffeners in automobile, the research is not in-depth.

However, in the real process of automobile sheet metal research, production and vehicle verification, it can be seen that stiffeners are very important for automobile applications. The scientific design and application of stiffener can improve the performance of automobile and production process, and the cost of improving performance is not high. In addition, the installation of stiffeners at inappropriate locations will lead to cracking and other damage, reducing the performance of the vehicle. Therefore, it is very important to design the stiffener of automobile sheet metal parts.

The function of automobile sheet metal stiffener

Enhanced NVH performance

The noise produced by automobile is one of the important reasons that affect the urban environment at present. The car needs to provide the driver with a good operating environment. NVH is a key standard that affects the overall level of automobile. NVH of automobile is one of the vehicle characteristics that the major automobile production companies and subsidiaries in the global automobile industry attach importance to. Among them, reducing the radiation power of the front partition and the vibration radiation noise to the seat cabin is an important indicator of NVH. The scientific design of stiffeners can improve this index. For example, the high value of Zui of the driver's ear is reduced from 130dB / N to 71db / N after the stiffeners are added to the middle part of the car's cowl panel and the wheel housings on both sides, which greatly improves the radiation power level of the front partition and the radiation sound pressure level of the driver's ear noise.

Enhanced strength performance

Strength refers to the ability of metal materials to never deform and fission under the pressure of force. The change of metal under the pressure of force mainly includes three continuous steps: elastic change, elastic-plastic change and fracture. When the pressure reaches the deformation limit, the metal will have a significant plastic change; when the pressure reaches the strength limit, the metal will break. Adding stiffeners in the appropriate area can increase the strength of the area and reduce the risk of failure.

Enhanced stiffness performance

Stiffness refers to the ability of metal or tissue to resist elastic deformation under compression. There is springback in bending parts, so it is necessary to increase the rigidity of deformation area when studying bending parts. For example, adding stiffeners at the turning position can improve the strength and rigidity of stamping parts and reduce the rebound. When stiffeners are added to the bracket, the rigidity of the part is enhanced and the springback is reduced.

Design key points and precautions

In the automobile sheet metal, it is not necessary to install stiffeners everywhere, nor to say that the effect is better if there are stiffeners. There are various functional requirements for automobiles. In some cases, the stiffeners can improve some functions and may also affect other functions. It is assumed that incorrect stiffeners are installed in the incorrect area, which may also cause overall damage to the vehicle. Therefore, in the design, it is necessary to pay attention to the application of stiffeners to the whole vehicle to avoid adverse effects. The following describes the key points and precautions for the design of stiffeners.

Direction of attention transfer

When it is necessary to install stiffeners to strengthen the parts, the orientation of the stiffeners must be consistent with the direction of the force; if it is necessary to partially weaken, it is necessary to pay attention to the direction perpendicular to the direction of the force, for example, crush the stiffeners. According to the force guidance, the same stiffener has different effects.

Understand the weak parts of stiffeners

The simple configuration of the stiffener Zui is a long strip of columns attached to the surface of the component in a straight line shape, in addition to the triangular ribs and so on. In fact, stiffeners of various shapes will be located in local vulnerable positions in the stamping process. Therefore, if it is not a special requirement, the stiffeners do not need to be connected with each other or too complex. Otherwise, there will be different manufacturing processes under various structural conditions. Complex stiffeners are more likely to produce fracture phenomenon than simple stiffeners, which will have adverse effects on vehicle performance. It has been proved that the reduction rate of steel plate through CAE analysis is 20% and above without reinforcement.

Master the structure and vehicle performance

In the design of sill beam and other supports, in order to enhance its supporting efficiency, there are the following methods: reduce Zui high bending moment, or apply scientific section shape to enhance the modulus of bending section. Therefore, the stiffener in the cavity area of the reinforced beam can not make the critical reinforced section change dramatically, otherwise it will reduce the performance; the stiffener should not make the section lower, which will cause the inertia moment of the section to be disturbed. Therefore, the cavity formed by the inner plate and the side wall of the doorsill shall be consistent, and the reinforcing rib of the inner plate shall face the interior rather than the exterior.